The function of MYMX (myomixer, myoblast fusion factor, Ensembl gene identifier ENSG00000262179) is as follows. Myoblast-specific protein that mediates myoblast fusion, an essential step for the formation of multi-nucleated muscle fibers (PubMed:28569745, PubMed:35642635). Involved in membrane fusion downstream of the lipid mixing step mediated by MYMK (By similarity). Acts by generating membrane stresses via its extracellular C-terminus, leading to drive fusion pore formation. Acts independently of MYMK (By similarity). Involved in skeletal muscle regeneration in response to injury by mediating the fusion of satellite cells, a population of muscle stem cells, with injured myofibers (By similarity). {ECO:0000250|UniProtKB:Q2Q5T5, ECO:0000269|PubMed:28569745, ECO:0000269|PubMed:35642635}.